The present invention relates generally to a one way drive device, and more particularly to a one way drive device which uses a dog clutch to transmit torque when driven in a torque transmitting direction and a ratchet clutch to provide an overrun function.
There are a variety of types of overrunning clutches including ratchet clutches, dog clutches, and traction type clutches such as roller ramp or sprag clutches. Each of the different types of clutches has certain advantages over the other types of clutches. For instance, for a given size clutch, applicant has found that dog clutches are generally better suited to transmit torque than ratchet and traction type clutches. This allows dog clutches to transmit loads which are larger then ratchet and traction type clutches are able to withstand. Applicant has also found that ratchet clutches generally provide a better overrun function and may be designed to provide extremely high overrunning speeds.
The present invention provides a novel one way drive device which uses a dog type clutch as a coupling arrangement to transmit torque and a ratchet type clutch to provide the overrun function and to move the dog clutch between the engaged and disengaged positions. Because the device does not rely on the ratchet clutch to transmit torque, the ratchet clutch may be designed to allow extremely high overrun speeds. When torque is required to be transmitted the dog clutch is used. This allows loads to be transmitted to an extent that a conventional ratchet clutch would not be able to withstand.